founder of the Seljuq dynasty, which ruled in Iran, Iraq, Syria, and Anatolia during the 11th– 14th centuries. Under his rule the Seljuqs assumed the leadership of the Islāmic world by establishing political mastery over the ʿAbbāsid caliphate in Baghdad.

The grandson of Seljuq, chief of the Oğuz tribes in the Jand region, Toghrïl, with his brother Chaghrï, entered Muslim Transoxania shortly before 1016, and in 1025 they and their uncle Arslan entered the service of the Turkish Qarakhanid prince of Bukhara. Defeated by Maḥmūd of Ghazna in the same year, Toghrïl and Chaghrï took refuge in Khwārezm (around the estuary of the Amu Darya 【river】, southeast of the Aral Sea), while Arslan settled in Khorāsān. Later, however, after their kinsmen in Khorāsān had been driven by Maḥmūd to western Iran, the two brothers themselves entered Khorāsān, where, having established close ties with the orthodox Muslim groups in the large towns, they subdued Merv and Nīshāpūr (1028–29). Finally, in 1040 at Dandānqān, the Seljuqs inflicted a decisive defeat on Maḥmūd's son Masʿūd. Khorāsān was then formed into a principality for Chaghrï, while Toghrïl was left free to conquer the Iranian plateau.

A methodical ruler, Toghrïl succeeded in building an empire by careful planning. The first conquests were generally made by the Turkmen raiders led by his foster brother Ibrāhīm Ināl. He himself then followed to administer the conquered territories. In this way, between 1040 and 1044, he occupied the Caspian areas of Khorāsān, Rayy, and Hamadan and established his suzerainty over Isfahan. In 1049 and 1054 he sent expeditions of Turkmens into the Byzantine lands of Anatolia, attempting to prevent Turkmen raids into the surrounding Muslim territories while at the same time increasing Seljuq power against the Byzantine Empire.

In 1055 Toghrïl, after conquering the principalities to the east and north of Iraq, entered Baghdad, where he was commissioned to overthrow the Shīʿī Fāṭimid caliphs of Cairo in Egypt and to restore, under the ʿAbbāsid caliph, the religious and political unity of the Islāmic world. A mounting threat from the Shīʿī and discontent among his supporters over administration and reward for services, however, resulted in a general uprising against Toghrïl. Prince Ināl with his Turkmens revolted in Mesopotamia and Iran, while a coalition of Arab and Shīʿī Būyid forces, financed and controlled by the Fāṭimids of Cairo and led by Basāsīrī, entered Baghdad (1058). The ʿAbbāsid caliph was imprisoned, and prayers were recited in the name of the Fāṭimid caliph of Cairo. Toghrïl then crushed the rebellion (1060), regained Baghdad, and pacified the Arabs of Mesopotamia. During his last years he fought the petty princes in northwest Iran and forced the Caliph to give him a daughter in marriage.